Apple's decision to fight a court order to help federal authorities unlock the iPhone of one of the San Bernardino shooters has been hailed by some of the biggest names in Silicon Valley who said complying could set a "troubling precedent."

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In a series of tweets on Wednesday, Google CEO Sundar Pichai warned that creating a backdoor for law enforcement to bypass security measures could compromise users' privacy.

"I have always admired Tim Cook for his stance on privacy and Apple's efforts to protect user data," Koum wrote on his Facebook page. "We must not allow this dangerous precedent to be set. Today our freedom and our liberty is at stake."

Brad Smith, Microsoft's president and chief legal officer, tweeted a link to a statement from Reform Government Surveillance, which is a coalition of tech companies, including Microsoft, which monitors government surveillance issues.

"Reform Government Surveillance companies believe it is extremely important to deter terrorists and criminals and to help law enforcement by processing legal orders for information in order to keep us all safe," the statement said. "But technology companies should not be required to build in backdoors to the technologies that keep their users’ information secure. RGS companies remain committed to providing law enforcement with the help it needs while protecting the security of their customers and their customers’ information."

In a letter posted Tuesday night, Cook said the FBI is essentially asking Apple to build a new operating system that could be installed on an iPhone recovered from an investigation. Such software does not exist today but Cook said if it did, there would be no way to guarantee it would only be used for investigations, putting the privacy of millions of Americans at risk.

"The government would have us remove security features and add new capabilities to the operating system, allowing a passcode to be input electronically," he said. "This would make it easier to unlock an iPhone by 'brute force' trying thousands or millions of combinations with the speed of a modern computer."

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